test: terminate test_manager properly

[mmta]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.02%. Comparing base (11509bd) to head (2fbd070).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #44      +/-   ##
==========================================
+ Coverage   95.52%   96.02%   +0.50%     
==========================================
  Files          27       28       +1     
  Lines        5586     5667      +81     
==========================================
+ Hits         5336     5442     +106     
+ Misses        250      225      -25     

Flag	Coverage Δ
unittests	96.02% <100.00%> (+0.50%)	⬆️

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Files	Coverage Δ
server/src/manager.rs	92.92% <100.00%> (ø)

... and 5 files with indirect coverage changes